Determination of heavy quark non-perturbative parametersfrom spectral moments in semileptonic B decays

Abstract.

Moments of the hadronic invariant mass and of the lepton energy spectra in semileptonic B decays have been determined with the data recorded by the DELPHI detector at LEP. From measurements of the inclusive b-hadron semileptonic decays, and imposing constraints from other measurements on b- and c-quark masses, the first three moments of the lepton energy distribution and of the hadronic mass distribution, have been used to determine parameters which enter into the extraction of |V _cb | from the measurement of the inclusive b-hadron semileptonic decay width. The values obtained in the kinetic scheme are:

$\begin{array}{*{20}l} {{m_{b} {\left( {1\;{\text{GeV}}} \right)}} \hfill} & { = \hfill} & {{4.591 \pm 0.062 \pm 0.039 \pm 0.005\;{\text{GeV/c}}^{2} ,} \hfill} \\ {{m_{c} {\left( {1\;{\text{GeV}}} \right)}} \hfill} & { = \hfill} & {{1.170 \pm 0.093 \pm 0.055 \pm 0.005\;{\text{GeV/c}}^{{\text{2}}} {\text{,}}} \hfill} \\ {{\mu ^{2}_{\pi } {\left( {1\;{\text{GeV}}} \right)}} \hfill} & { = \hfill} & {{0.399 \pm 0.048 \pm 0.034 \pm 0.087\;{\text{GeV}}^{{\text{2}}} {\text{,}}} \hfill} \\ {{ \ifmmode\expandafter\tilde\else\expandafter\~\fi{\rho }^{3}_{D} } \hfill} & { = \hfill} & {{0.053 \pm 0.017 \pm 0.011 \pm 0.026\;{\text{GeV}}^{{\text{3}}} ,} \hfill} \\ \end{array}$

and include corrections at order 1/m _b ³. Using these results, and present measurements of the inclusive semileptonic decay partial width of b-hadrons at LEP, an accurate determination of |V _cb | is obtained: ${\left| {V_{{cb}} } \right|} = 0.0421 \times {\left( {1 \pm 0.014_{{{\text{meas}}{\text{.}}}} \pm 0.014_{{{\text{fit}}}} \pm 0.015_{{{\text{th}}{\text{.}}}} } \right)}$